Anaerobic respiration
Exam-ready definition
The chemical reactions in cells that break down glucose without oxygen, releasing much less energy than aerobic respiration. In muscles: glucose → lactic acid. In yeast: glucose → alcohol + carbon dioxide.
How this is marked
Know both equations and the comparison: less energy released per glucose than aerobic. 'Oxygen debt' (lactic acid removal after exercise) is a favourite Extended question.
In an exam answer
Explaining muscle fatigue in a sprint: 'When oxygen runs short, the muscles respire anaerobically, breaking glucose into lactic acid and releasing a small amount of energy.'
Full topic guide: Respiration
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